Make storing and displaying application used to toot opt-in

app/serializers/rest/status_serializer.rb

@@ -14,7 +14,7 @@ class REST::StatusSerializer < ActiveModel::Serializer
   attribute :local_only if :local?
 
   belongs_to :reblog, serializer: REST::StatusSerializer
-  belongs_to :application
+  belongs_to :application, if: :user_shows_application?
   belongs_to :account, serializer: REST::AccountSerializer
 
   has_many :media_attachments, serializer: REST::MediaAttachmentSerializer
@@ -40,6 +40,10 @@ class REST::StatusSerializer < ActiveModel::Serializer
     !current_user.nil?
   end
 
+  def user_shows_application?
+    object.account.user_shows_application?
+  end
+
   def visibility
     # This visibility is masked behind "private"
     # to avoid API changes because there are no